One of the regiments of the Imperial & Royal Army, it appears in a number of stories, principally "The Thin Line" and "...Is In Another Castle."

It is a standard regiment of foot within the I&RA, meaning that it tends to be armed with spears and short-swords; it is observed by Westersloe Winterbough V that the use of the elven bow had been declining in regiments of the line.

During the events of The Thin Line, the regiment is deployed to the border with the United Cities, as a means of supporting that realm and guarding the frontier against the Grand Duchy of the Grey Horde. Thorn Platoon of the 37th Regiment, specifically, is guarding the river crossing at the remote village of Mossford, while the rest of the Regiment appears to have been stationed in and around the larger village of Flourford, downstream.

The Regiment fights furiously during the twin battle of Flourford-Mossford, an action which sees multiple Valour Medals awarded to the Regiment; a battle honour is also added to its standard. At this point, because of the sighting of the comet "Fuma's Tail" a few days before the battle, it gets its nickname "The Comet Regiment." Squaddies within the Regiment take to wearing a small silver comet-badge upon their uniform, a decidedly non-regulation affectation.

The 37th Regiment also takes part in the rescuing of Princess Anastasia of Licksburg, when she is abducted by Baron Virginianus in "...Is In Another Castle." This operation, unlike Flourford-Mossford, does not incur any casualties, and the Auld Sweats of the Regiment are given King's Bounty of booze, much to their delight.

Winterbough, though not officially a member of the Regiment, is considered by the squaddies of the Regiment to belong to it by right of his efforts at Flourford-Mossford. Winterbough does wear the Comet Badge upon his uniform, to the slight irritation of his liege-lord, Prince Roland.